Decarburization of Fe–C droplet was investigated by fluid dynamics numerical simulation based on physical properties under gas phase mass transfer controlled regime. Fluid flow and species concentration fields around the droplet implementing a reaction of carbon with oxidant gas at the interface were calculated by a commercial CFD package which solves a set of transport equations. Overall decarburization rate of the molten Fe–C droplet was obtained by the simulation, and it was additionally validated by the present authors’ own experiment using gas-liquid drop reaction in a levitation melting equipment. It was observed by the simulation that decarburization rate on the surface of a droplet was not homogeneous due to inhomogeneous gas distribution around the droplet. A new concept of local mass transfer coefficient ratio was proposed in the present study as a ratio of effective local mass transfer coefficient at a specific site over average mass transfer coefficient, as a function of θ (angle between direction of gas flow and direction to reaction site on the droplet surface from the droplet center) and dimensionless numbers regarding fluid flow:Furthermore, effect of distance between two droplets was investigated by the present numerical model for decarburization of multiple droplets. The local mass transfer coefficient was found to have a significant impact on decarburization rate of a droplet when the other droplet locates very close. Relation between decarburization rate of two droplets and distance between them were analyzed.